1. Field
The disclosed embodiments belong to the field of airplanes comprising a wing fixed to the fuselage.
2. Brief Description of Related Developments
In particular, the disclosed embodiments relate to an airplane architecture in which the fuselage is designed to allow optimum loading of the various payloads, passengers, goods, fuel, etc.
In order to produce airplanes, particularly those with large loading capacity, without detracting from the speed performance and operational capabilities, there are various solutions that have been conceived.
A first solution is that of a conventional airplane architecture, that is to say one with a fuselage that is cylindrical over an essential part of its length and to which the airplane wing is fixed. In this case, to increase the carrying capacity of the airplane, the dimensions of the fuselage are increased either by lengthening the cylindrical part of the fuselage or by increasing the cylindrical cross section of the fuselage.
Lengthening the cylindrical part of the fuselage is generally the most suitable solution and the most widespread solution for creating a version of an existing model of airplane the capacity of which is to be increased. Examples of such airplane versions in which the capacity has been increased by lengthening the cylindrical part of the fuselage are numerous. By way of example, mention may be made of the Airbus 8321 the fuselage of which has been lengthened from the basic A320 version, or alternatively, the Boeing B737 of which the successive versions from the B737-100 to the B737-900 have had their fuselages lengthened without changing the cross section of the cylindrical part in order to increase the passenger-carrying capacity.
While a solution such as this is advantageous for increasing the capacity of an existing model of aircraft by creating a new version economically, it allows only a limited increase because of the constraints imposed by the initial design and, in particular, by the cross section of the cylindrical part of the fuselage the length of which cannot reasonably be increased beyond certain structural and operational limits.
A second known solution, also based on a conventional airplane architecture is, when designing an airplane, to define a larger cross section of the cylindrical part of the fuselage in order to increase the available volume in which a payload can be carried.
In order to avoid excessively increasing the diameters of the cylindrical sections of circular cross section in which the available volume is not easy to use optimally above certain diameters, the cross sections of the cylindrical part are either taller than they are wide, for example like on the Airbus A380 or the Boeing 737, or wider than they are tall as proposed in patent FR 1 460 060.
In these cases, the shape of the cross section of the fuselage is obtained more or less by superposing or by juxtaposing two sections close to sections corresponding substantially to parts of circles, known as lobes, determining compartmentalized regions, and the ratio between the height and the width of the fuselage is then less than 2 when the lobes are superposed or greater than 0.5 when the lobes are juxtaposed given the theoretical region of overlap of the two lobes.
Although this method makes it possible to obtain airplanes with appreciably improved carrying capacity without jeopardizing the other conventional characteristics of the airplane, it does have the disadvantage, on the one hand, of creating compartmentalized regions in the fuselage, these being dictated by the layout of the lobes, which has the effect of limiting the loading options and, on the other hand, of maintaining numerous design constraints as regards in particular the power plants, the landing gear, the loading means and other auxiliaries needed or useful in operating the airplane, these being constraints that are known on conventional airplanes in general but which are exacerbated by the dimensions of the airplanes when greater carrying capacities are being sought.
A third solution is to use the flying wing principle, that is to say the principle of an airplane with no distinct fuselage but which has a wing the central part of which is very much thicker in order to create in this central part a volume needed for carrying the payload. This type of architecture has, however, led to industrial embodiments only under exceptional circumstances.
One problem with flying wings is connected with where to install the power plants which have both not to create unacceptable aerodynamic penalties, not to limit the design of the other parts of the airplane, the fuselage, the landing gear and the exits for example, and not to present particular problems of maintenance, these being constraints that are difficult to limit when the engines are fixed under the wing or in the thickness thereof as in known embodiments.
Another problem stems from the difficulty in locating a sufficient number of exits for loading and offloading passengers or goods, because the cabin region of a flying wing is vast in terms of surface area and in terms of volume whereas the region situated around the perimeter of this cabin and in which the exits can be sited are limited and are further positioned, in part, in the leading edge of the wing in regions with great curvature and which are subjected to severe structural and aerodynamic loadings.
Another problem is concerned with the difficulty during loading and during flight of controlling the position of the center of gravity of the airplane which needs to be kept in a relatively restricted region whereas the loading area is, for its part, over a wide area.
Furthermore, this type of flying wing architecture is very far removed from the so-called conventional architectures of present day airplanes and even nowadays still comes up against prejudice which tends to reject the use of solutions which differ so much from the solutions currently in use.
It should therefore be noted that no overall airplane architecture that escapes from the constraints of conventional cylindrical-body airplanes has been proposed for producing an airplane, particularly a large capacity transport airplane, and solving the numerous problems presented by designing and operating such an airplane.